Light moulded masses, light concrete and light plasters containing granules of expanded thermoplastic resins, have numerous applications: manufacture of prefabricated parts such as: slabs, parpens, studs, rough masonry, various boxes, drain pipes and plates, bridge parts, underlay for roads, posts, insulation panels, partition walls, chimney stacks, etc.
Poured on site into shuttering and in pavings and cappings, they likewise find numerous applications in building construction and civil engineering.
The presence of expanded thermoplastic resin granules distributed in the mass confers upon this material besides a range of density running from 100 kg/m.sup.3 up to the weight of normal concrete, and similarly for plaster, new qualities of heat and sound insulation, insulation against moisture and against the propagation of fire.
In the manufacture of these materials it is found that the expanded thermoplastic resin granules are water-repellant and have a very low density, for certain expanded thermoplastic resins less than 10 kg/m.sup.3. Under these conditions the expanded thermoplastic resin granules just as they are, are difficult to mix in a homogeneous fashion in mortar or in plaster.
In order to take this fact into account a two-stage process has been proposed for mortar.
In a first operation the expanded thermoplastic resin granules are precoated with a mixture of epoxy and/or epikote and laromin resins emulsified in water, expanded thermoplastic resin granules, cement and volcanic ash are then dried.
In a second operation the granules thus coated are mixed with cement, sand, and water in order to prepare a light concrete.
This method is very costly, firstly because it needs two operations, secondly because of the very high cost of the resins employed. The result is that the use of this material is very much restricted.